Photonic crystals (PCs) are materials with a periodic modulation in refractive index. If the band-gap of a photonic crystal is located at a visible wavelength, the photonic crystals can produce so-called “structural colors”. Current research in the field is directed at structural colors and their related properties (such as properties arising in the wavelength ranges of ultraviolet (UV) light, visible light, and infrared (IR) light) using both inorganic and organic materials. Thus, there is a need for photonic crystals that can be bio-compatible and/or bio-degradable, for example.
Furthermore, with reference to the textile industry, it is known that coloring or dyeing of fabrics and especially silk fabrics is challenging. In addition, color fading due to leaching or oxidation/bleaching is a typical problem in the industry. There are also significant challenges for placing structural colors on fabric. One problem is that structural colors typically do not spread well on fabric. Another problem is that structural colors typically do not adhere to fabric.